The ability to be able to accomplish continuously variable power transmission is extremely desirable in many power applications, but mainly in the automotive field where its introduction would provide advantages including a considerable increase in fuel economy, a large increase in engine braking ability, the potential of using a constant speed engine resulting in lower exhaust emissions, and the availability of a greater range of high to low ratio. Variable ratio drives of a mechanical nature have been available for industrial use involving relatively small horse powers for many years Efforts have been made to use these same devices on automobiles, but without success, primarily because of the high torques and wide range of speeds associated with the internal combustion engine.
The more recent designs have consisted of adjustable conical pulleys connected by means of a metal belt which, together transmit power by utilizing metallic traction, that is the engaging surfaces are pressed together to the extend that all lubrication is excluded, and the coefficient of friction approaches unity. However, these designs fail to achieve this condition, because the pulleys, whose two halves slide on a splined shaft and are located by mechanical or hydraulic means, display insufficient rigidity. Also, especially at extreme ratios, the arc of contact being the arc over which the belt engages a pulley at any one time and which determines the power transmitting capability of all belt and pulley systems, becomes minimal, resulting in slippage.